Variable buoyancy control system

ABSTRACT

A VARIABLE BUOYANCY CONTROL SYSTEM FOR AN UNDERWATER VEHICLE INCLUDING A BUOYANCY TANK, A MAIN FLUID PRESSURE LINE WHICH IS CONNECTED TO THE TANK, THE TANK, HAVING TOP AND BOTTOM BUTTERFLY VALVES, MEANS FOR SELECTIVELY OPENING AND CLOSING THE TOP AND BOTTOM BUTTERFLY VALVES, A FLOW CONTROL VALVE CONNECTED IN THE FLUID PRESSURE LINE FOR SELECTIVELY CONTROLLING THE FLUID PRESSURE TO THE TANK, A RELIEF VALVE MOUNTED IN THE BUOYANCY TANK FOR RELIEVING PRESSURE FROM THE TANK UPON THE OCCURRENCE OF POSITIVE PRESSURE DIFFERENTIAL OF THE TANK OVER AMBIENT, A SECONDARY FLUID PRESSURE LINE CONNECTED TO THE MAIN FLUID PRESSURE LINE ACROSS SAID FLOW CONTROL VALVE, AND A DEPTH COMPENSATOR VALVE CONNECTED IN THE SECONDARY FLUID PRESSURE LINE AND PRESSURE RESPONSIVE TO THE BUOYANCY TANK AND AMBIENT WATER FOR BY-PASSING FLUID TO THE BUOYANCY TANK UPON THE OCCURRENCE OF A NEGATIVE PRESSURE DIFFERENTIAL BETWEEN THE TANK AND AMBIENT.   D R A W I N G

Feb. 13, 1973 A T STRICKLAND VARIABLE BUOYANCY CONTROL SYSTEM Filed NOV. 24

ERWA/ COA/MSTQM #rra/@vsn United States Patent O U.S. Cl. 114--16 E 8 Claims ABSTRACT OF THE DISCLOSURE A variable buoyancy control system for an underwater vehicle including a buoyancy tank; a main uid pressure line which is connected to the tank; the tank having top and bottom butterfly valves; means for selectively opening and closing the top and bottom butterfly valves; a flow control valve connected in the liuid pressure line for selectively controlling the -uid pressure to the tan-k; a relief valve mounted in the buoyancy tank for relieving pressure from the tank upon the occurrence of positive pressure differential of the tank over ambient; a secondary uid pressure line connected to the main fluid pressure line across said flow control valve; and a depth compensator valve connected in the secondary huid pressure line and pressure responsive to the buoyancy tank and ambient water for by-passing fluid to the buoyancy tank upon the occurrence of a negative pressure ditferential between the tank and ambient.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION The present invention relates to a variable buoyancy control system which includes a buoyancy tank for an underwater vehicle wherein the tank is automatically pressure compensated and can be selectively ballasted and deballasted with ambient water.

DESCRIPTION OF THE PRIOR ART In Pat. No. 3,434,443 to Estabrook there is shown an underwater buoyancy transport vehicle which is operated by a diver for lifting and transferring loads within the ocean. This vehicle has thrusters for propelling the vehicle in desired directions and a variable buoyancy control system including a buoyancy tank for ascending or descending the vehicle with or Without its payload. In the patent the buoyancy tank is described as having top and bottom butterlly valves and a pressure line from the surface for selectively ballasting and deballasting the tank. An improved ballasting and deballasting system was required so that the vehicle would be self contained and not be constrained by a tethered pressure line to the oceans surface. Further, `since the vehicle transcends various depths and undergoes various pressures, it became desirable that the buoyancy tank be automatically pressure compensated whether it ascends or descends. Without pressure compensation an opening of either butterfly valve after some descent will cause a rapid rush of water into the buoyancy tank because of the greater ocean pressure. This can cause the vehicle to drop uncontrollably in the ocean. An opposite effect occurs upon ascent when the bottom buttery valve is opened. Also, pressure compensation enables the buoyancy tank to be constructed of minimum wall thickness and the diver can relieve his mind of pressure compensation while he s operating the vehicle. The prior art did not demonstrate an embodiment which would provide these advantages.

3,716,009 Patented Feb. 13, 1973 The present invention provides a variable buoyancy control system which is especially adapted for use on an underwater vehicle, such as the buoyancy transport vehicle described in the aforementioned patent. This control system includes a buoyancy tank which has the primary advantage of being automatically pressure compensated whether the vehicle ascends or descends in the water. The buoyancy control system i'mcludes the buoyancy tank; a main fluid pressure line which is connected to the tank; the tank having top and bottom butterfly valves; means for selectively yopening and closing the butterfly valves; a il'ow control valve connected in the main iluid pressure line for selectively controlling the fluid pressure to the tank; a relief valve mounted in the buoyancy tank for relieving pressure from the tank upon the occurrence of a positive pressure differential of the tank over ambient; a secondary lluid pressure line connected to the main uid pressure line across the ilow control valve; and a depth compensator valve connected in the secondary fluid pressure line and pressure responsive to the buoyancy tank and ambient water for by-passing lluid to the buoyancy tank upon the occurrence of a negative pressure differential between the tank and ambient.

STATEMENT OF THE OBJECTS OF THE INVENTION An object of the present invention is to provide an automatically pressure compensated variable buoyancy control system for an underwater vehicle.

Another object is to provide a buoyancy control system for a tank which has top and bottom butteriiy valves wherein the system enables fine control of buoyancy of the tank when the butterfly valves are selectively opened and closed.

A further object is to provide a variable buoyancy control system Which is adapted for self contained utilization on an underwater vehicle, and which includes a buoyancy tank which can be constructed of a minimum wall thickness and thereby minimum weight.

Other objects and many of the attendant advantages of this invention will be readily appreciated as it becomes better understood by reference tothe description and accompanying drawings which follow.

BRIEF DESCRIPTION vOF THE DRAWING FIG. 1 is a schematic illustration of the variable buoyancy control system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 there is shown therein a variable buoyancy control system 10 which includes a buoyancy tank 12, which may be spherical, and a main fluid pressure line 14 which has an inlet 16 and an outlet 18, the inlet being adapted to receive uid and the outlet opening into the buoyancy tank 12 for introducing pressurized fluid therein. The buoyancy tank 12 has top and bottom butterfly valves r20 and 22 respectively, and means are provided for selectively opening and closing these buttery valves so as to allow water to enter and exit the buoyancy tank. The opening and closing means may include hydraulic rotary actuators 24 and 26 which are connected to the pivot shafts of the top and bottom butterily valves 20 and 22 respectively, and hydraulic lines 28 and 30 which slave the hydraulic rotary actuators 24 and 26 respectively to linear actuators 32 and 34 respectively. The linear actuators 32 and 34 in turn have control handles 36 and 38 which can be controlled by a diver for selectively opening and closing the butterfly valves 20 and 22. For further control by the diver there is provided a flow control valve 40 which is connected in the main fluid pressure line 14 for selectively controlling the fluid pressure to the buoyancy tank 12 so as to ascend or descend the vehicle depending upon the positions of the butterfly valves 20 and 22. The flow control valve 40 may be operated by a handle 42.

It is desirable that the buoyancy tank be constructed of minimum wall thickness so that it will be as light as possible. In this manner, the lifting capacity of the buoyancy tank will be optimized. While separate controls could have been provided for the driver to pressure compensate the tank it is more desirable that the tank be automatically pressure compensated upon ascent or descent and that the diver be freed of this additional responsibility. This has been accomplished by providing the wall of the buoyancy tank with a relief valve 44 which is capable of relieving pressure from the tank when there is a positive pressure differential of the tank pressure over ambient ocean pressure. Further, a secondary fluid pressure line 46 is connected to the main fluid pressure line 14 across the flow control valve 40. A depth compensator valve 48 is connected in the secondary fluid pressure line 46 and is mounted to the tank 12 in communication with its interior and ambient pressure so as to be pressure responsive to both the buoyancy tank and ambient water for by-passing fluid to the buoyancy tank 12 upon the occurrence of a negative pressure differential between the tank and ambient. Accordingly, when the buoyancy tank 12 ascends to a lesser pressure the pressure within the tank is vented through the relief valve 44, and when the buoyancy tank descends to a higher pressure the depth compensator 48 senses this condition and opens the secondary fluid pressure line 46 to introduce fluid for raising the pressure within the tank.

In the preferred embodiment of the invention the buoyancy control system utilizes hydrazine as the working fluid. In order to convert the hydrazine into a pressurized gas, a gas generator 50 is mounted in the main fluid line 14 between the buoyancy tank 12 and both legs of the secondary fluid pressure line 46. In order to limit the maximum flow of the hydrazine through the flow control valve 40 and thereby achieve fine trimming adjustments of the buoyancy of the tank 12 a rate orifice valve 52 is disposed in the main fluid pressure line 14 between the gas generator 50 and both legs of the secondary fluid pressure line 46.

The gas generator 50 contains a catalyst bed where the hydrazine is catalytically decomposed into hydrogen, nitrogen, and ammonia. This process is exotheromic and results in a gas generator exhaust gas temperature exceeding 1,000o F. On the inlet side of the gas generator and in the main fluid pressure line 14 there is disposed a check valve 54 for preventing the generated gases from exiting upstream thereof. The main fluid pressure line 14 extends from the outlet of the gas generator into the buoyancy tank 12 and extends upwardly terminating in the outlet or outlets 18 which may take the configuration of a pair of stove pipes. Disposed in the main fluid pressure line 14 is another check valve y56 just below the outlets 18 and within the buoyancy tank. Since the generated gases are extremely hot the extension of the main fluid pressure line between the gas generator `t] and the check valve 56 will reduce the temperature so as to protect the check valve 56.

The buoyancy control system may further include a fuel delivery means which is generally shown in the top portion of FIG. 1. The fuel delivery means may include a container 56 with a fuel bag 58 therein for containing the hydrazine fuel. The fuel bag 58 has an outlet which is connected to the inlet 16 of the main fluid pressure line. A pump 60 has an inlet 61 to ambient water and an outlet which is connected by a water line 62 to the container 56 so as to apply water pressure to the fuel bag 58 within the container. Battery power means 64 may be provided for operating the pump and a push button limit switch 66 may be provided for turning the power means on and off. An accumulator 68 in the water line 62 may be provided with a plunger 70 for turning the limit switch on when water pressure in the accumulator and container drops below a predetermined value and turning the limit switch off when the water pressure in the accumulator and container are at said predetermined value. Accordingly, a constant pressure is maintained on the fuel bag 58 to supply hydrazine under pressure to the flow control valve 40 and the pressure compensator valve 418. The fuel delivery means is described in more detail in a co-pending application Ser. No. 187,484 entitled Constant Pressure Liquid Supply System by Alvah T. Strickland.

OPERATION OF THE INVENTION The diver adjusts the buoyancy of the tank 12 by selectively controlling the three control handles 36, 38, and 42. To decrease the tan-ks buoyancy, in order to descend, the top butterfly valve 20 is opened, the bottom butterfly valve 22 is closed, and the flow control valve 40 is closed. If a rapid decrease in buoyancy is required the diver will also open the bottom butterfly valve 22. If the diver desires to increase the buoyancy of the tank in order to ascend, the top butterfly valve 20 is closed, the bottom butterfly valve 22 is opened, and the flow control valve 40 is opened. When a static condition is desired (maintaining trim) all of the valves are placed in a closed position. If the buoyancy tank is partially above the water line and the operator desires to descend, both butterfly valves 20 and 22 will be opened while the flow control valve 40 is closed. When the rate orifice valve 52 is open the above changes can be made quickly and when this valve is closed, buoyancy increases are made more slowly, which is desirable for close positioning of the buoyancy tank.

It is now readily apparent that the present invention provides a unique arrangement of components for enabling a change of buoyancy in an underwater vehicle with minimum control by the diver. By automatic pressure compensation of the buoyancy tank the divers mind is relieved of this responsibility and the tank can be constructed of minimum wall thickness.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim:

1. A variable buoyancy control system for an underwater vehicle comprising:

a buoyancy tank;

a main fluid pressure line having an inlet and an outlet,

the inlet being adapted to receive fluid and the outlet opening into the buoyancy tank for introducing pressurized fluid therein;

said buoyancy tank having top and bottom butterfly valves;

means for selectively opening and closing said top and bottom butterfly valves so as to allow water to enter and exit the buoyancy tank;

a flow control valve connected in the main fluid pressure line for selectively controlling the fluid pressure to said tank so as to ascend or descend the vehicle depending upon the positions of the butterfly valves;

a relief valve mounted in the buoyancy tank for relieving pressure from the tank upon the occurrence of a positive pressure differential of the tank over ambient;

a secondary fluid pressure line connected to the main fluid pressure line across said flow control valve; and

a depth compensator valve connected in the secondary fluid pressure line and pressure responsive to the buoyancy tank and ambient water for by-passing fluid to the buoyancy tank upon the occurrence of a negative pressure differential between the tank and ambient.

2. A variable buoyancy control system as claimed in claim 1 including:

a gas generator mounted in the main fluid line between the buoyancy tank and both legs of the secondary fluid pressure line.

3. A variable buoyancy control system as claim in claim 2 including:

a rate orice valve disposed in the main fluid pressure line between the gas generator and ow control valve for limiting maximum flow through the flow control Ivalve.

4. A variable buoyancy control system as claimed in claim 2 including:

the main Huid pressure line extending upwardly within buoyancy tank; and

a check valve disposed in the main fluid pressure line upstream from the gas generator and another check valve disposed in the main uid pressure line within the buoyancy tank.

5. A variable buoyancy control system as claimed in claim 2 wherein fuel delivering means includes:

a container with a fuel bag disposed therein, said fuel bag having an outlet which is connected to the inlet 25 switch on when water pressure in the accumulator and container drops below a predetermined value and turning said switch off when the 'water pressure in the accumulator and container are at said predetermined value. 6. A variable buoyancy control system as claimed in claim 5 including:

a rate orifice valve disposed in the main fluid line between the gas generator and the llow control valve. 7. A variable buoyancy control system as claimed in claim 6 including:

the main iluid pressure line extending upwardly within the buoyancy tank; and a check valve disposed in the main fluid pressure line upstream from the gas generator and another check valve disposed in the main uid pressure line within the buoyancy tank. 8. A variable buoyancy control system as claimed in claim 7 including:

said fuel;

the fuel being hydrazine and being disposed in said fuel bag.

References Cited UNITED STATES PATENTS 30 MILTON BUCHLER, Primary Examiner G. L. BAREFOOT, Assistant Examiner U.S. C1. X.R. 137-110 

